Sonic Frontiers SFS-50 Tube Power Amp Reviewed

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Rules are meant to be broken. This time, it's our policy of not reviewing product without UK distribution. On occasion, we make exceptions, and the Sonic Frontiers SFS-50 valve amplifier is the sort of product which qualifies as a special case.

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It's not as if the world is shy of decent valve amplifiers. So varied is the current selection that you can find something from under #500 on up to #20,000, Class-A, Class-B and all points inbetween, monoblocks, stereo units, four-chassis set-ups, OTLs, hybrids -- take your pick. But we just can't get enough of the utilitarian, no-frills work horses, the ones which seem to eschew the fairy dust. In other words, I'll always champion an amplifier which comes across like a latter-day Radford STA-25, Quad II or Dynaco Stereo 70.

The former lives on in the current range of Woodside descendants, the Dynaco is back in production and you can still find decent Quad IIs for sensible prices. What Sonic Frontiers offers is a mix of the good old fashioned virtues but with more grunt and more high-end applicability. So when the company offered to send one over to HFN/RR, despite the lack of a British presence, we couldn't say 'No'. And when we found out that they make 240V export versions, sell direct from the factory if you live in a country without a distributor, that the price is a mere $2195 in US funds (plus whatever it costs to ship 25kg), that they accept Mastercard and Visa and offer a five year warranty plus six months on the valves, well, we sort of owed it to you.

Sonic Frontiers, though, is not an American company. It's Canadian. Considering that the country has been making great strides in high-end manufacture over the past decade -- Classe, Oracle, Museatex and so on -- the appeal was guaranteed. Best of all, it appears that the guys at Sonic Frontiers have their hearts in the right place, admitting to being inspired by Dynaco's classic tube products. Which is why they offer their amps in kit form for a 30% saving.

Equally impressive is their choice of a 'semi' hired gun. Their collaborator is Joe Curcio, well-known to readers of the tube bible, Glass Audio, and one of the most highly-respected tube designers at work today. Among his triumphs are some modifications to the Dynaco Stereo 70, the work reflected in the design of the SFS-50. Sonic Frontiers sought his permission to incorporate some of his work and Joe lent a hand.

The SFS-50 is a tube lover's vision, all function but without any rough edges. The laboratory look starts with the satin-chrome chassis, a healthy 18in wide and 14.5in deep, standing 9in tall with the valve cage in place. The company recommends using the amplifier without the black tube cover for better ventilation; it's provided as a sop to parents and pet-owners. The transformers are finished in black with chrome caps and the sloped front panel contains an on/off switch a gold-coloured centre panel and a large meter for bias setting.

At the back are Tiffany phono inputs and chunky copper Edison Price binding posts which accept thick bare wire, spades or -- in a pinch -- banana plugs in the spaces designed for bare wire. In the area covered by the cage are two matched pairs of KT-88s (the company has been using Gold Aero tubes exclusively since September 1991), four 6DJ8s and four large capacitors. Between the banks of valves is a small rotary which selects each of the four output tubes for bias adjustment.

All this requires is a screwdriver. Switch on, leave the amp to settle in for a few minutes and dial in each valve. Next to each one is a set screw, which you turn until the needle on the meter reaches '50'. That's it.

The basic concept is one which has worked well for a number of tube revivalists, blending the tried-and-tested with the modern. The power supply is of the over-kill variety, conservatively rated and regulated 'where appropriate', with 1000uF of main filter capacitance, filter choke and custom-made shunt capacitors. The output transformers are custom-made, with a core of grain-oriented silicon steel.

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